case vessel code n-729-1 2005. this means that · case cases of asme boiler and pressure vessel...

CASE

N-729-1CASES OF ASME BOILER AND PRESSURE VESSEL CODE

Approval Date: March 28, 2006

The ASME Boiler and Pressure Vessel Standards Committee took action toeliminate Code Case expiration dates effective March 11, 2005. This means thatall Code Cases listed in this Supplement and beyond will remain available for

use until annulled by the ASME Boiler and Pressure Vessel Standards Committee.

Case N-729-1Alternative Examination Requirements for PWRReactor Vessel Upper Heads With Nozzles HavingPressure-Retaining Partial-Penetration WeldsSection XI, Division 1

Inquiry: What alternative examination requirementsto those of Table IWB-2500-1, Examination CategoryB-P (1980 Edition through the 2004 Edition) and Exami-nation Category B-E (1980 Edition through the 1992Edition), IWB-2200, IWB-2400, and IWB-3000, may beused for PWR reactor vessel upper heads with nozzleshaving pressure-retaining partial-penetration welds?

Reply: It is the opinion of the Committee that thefollowing alternatives to the requirements of TableIWB-2500-1, Examination Category B-P (1980 Editionthrough the 2004 Edition) and Examination CategoryB-E (1980 Edition through the 1992 Edition), IWB-2200,IWB-2400, and IWB-3000, may be used for PWR reactorvessel upper heads with nozzles having pressure-retainingpartial-penetration welds.

-1000 SCOPE AND RESPONSIBILITY

-1100 SCOPE

This Case provides alternative requirements for exami-nation of PWR reactor vessel upper heads with nozzleshaving pressure-retaining partial-penetration welds.

-1200 COMPONENTS SUBJECT TOEXAMINATION

-1210 EXAMINATION REQUIREMENTS

The examination requirements shall apply to thefollowing:

(a) Heads having nozzles fabricated from UNSN06600 material with UNS N06082 or UNS W86182partial-penetration welds.

(b) Heads having nozzles fabricated from PrimaryWater Stress Corrosion Cracking (PWSCC) resistantmaterials, such as UNS N06690 base metal with UNSN06052 or UNS W86152 partial-penetration welds.

-2000 EXAMINATION AND INSPECTION

-2200 PRESERVICE EXAMINATION

-2210 BASELINE EXAMINATION

The examinations listed in Table 1 shall be performedcompletely, once, as a baseline examination. These exam-inations shall include all nozzles. Examinations per-formed prior to implementation of this Case that meetthe requirements of Table 1 may be credited.

-2220 PRESERVICE EXAMINATION AFTERREPAIR/REPLACEMENT ACTIVITIES

Prior to return to service, the applicable volumetricand surface examinations listed in Table 1 shall be per-formed on items affected by the repair/replacementactivity.

-2400 INSPECTION SCHEDULE

-2410 INSPECTION PROGRAM

Inservice examination methods and frequency, asrequired by Table 1, shall be determined using the follow-ing parameters to characterize the susceptibility to crackinitiation and the potential for crack propagation:

(a) Susceptibility to crack initiation is represented bythe EDY parameter, calculated as follows:

EDY n {AEFPY2 exp[-Q9i( T~d )I.L R thed T'<a<<;

J= I

(b) Potential for crack propagation is represented bythe RIY parameter, calculated as follows:

E

The Committee's function is to establish rules of safety, relating only to pressure integrity, governing the construction of boilers, pressure vessels, transport tanksand nuclear components, and inservice inspection for pressure integrity of nuclear components and transport tanks, and to interpret these rules when questions ariseregarding their intent. This Code does not address other safety issues relating to the construction of boilers, pressure vessels, transport tanks and nuclear components,and the inservice inspection of nuclear components and transport tanks. The user of the Code should refer to other pertinent codes, standards, laws, regulations orother relevant documents.

I (N-729-1) SUPP 8 - NC

CASE (continued)

N-729-1 CASES OF ASME BOILER AND PRESSURE VESSEL CODE

0n2RIY= E fAEFPYj exp[--• T -

eL [__&(ha ef!Jj=nl

where

EDY = total effective degradation years, normal-ized to a reference temperature of1059.67R (588.71K)

AEFPYj = effective full power years accumulatedduring time periodj

Qg = activation energy for crack growth= 31 kcallmol (130 kJ/mol)

ai = activation energy for crack initiation= 50 kcal/mol (209 kJ/mol)

R = universal gas constant= 1.103 X 10-3 kcal/mol-R (8.314 J/mol K)

RIY = reinspection years, normalized to a refer-ence temperature of 1059.67R (588.71K)

Theadj = 100% power head temperature during timeperiod j

Tref = reference temperature= 1059.67R (588.71K)

n = number of time periods with distinct 100%power head temperature since initial headoperation

nl = number of the first time period with dis-tinct 100% power head temperature1 sincetime of most recent volumetric or sur-face NDE

n2 = number of the most recent time periodwith distinct 100% power headtemperature

1

-2420 SUCCESSIVE EXAMINATIONS

(a) If a component is accepted by evaluation for con-tinued service in accordance with -3132.3, the areas con-taining the flaws shall be reexamined prior to the end ofthe evaluation period used in the flaw evaluation. If theprovisions of Table 1 do not require reexamination ofthe areas containing the flaws at least once per inspectionperiod, a reexamination shall be performed during thenext three inspection periods listed in the schedule of theinspection program of IWA-2400.

(b) If the reexaminations required by -2420(a) revealthat the flaws remain essentially unchanged for threesuccessive examinations, the component examination

1 Head temperature at 100% power may have been changed duringthe life of the plant due to design changes, power uprates, etc., and thesummation is over the number of distinct periods, either since initialhead operation for EDY or since the last volumetric or surface NDEfor RIY.

schedule may revert to the schedule of examinations iden-tified in Table 1.

-2430 ADDITIONAL EXAMINATIONS

If an examination performed in accordance withTable 1 or -2420 reveals a leak or a flaw not acceptablefor continued service in accordance with the provisionsof -3132.3, a Level 3 examination in accordance withTable 1 [Note (6)] shall be performed on all items of thatItem Number prior to return to service. Additionally, avisual examination in accordance with Table 1 [Note (1)](VE throughout this Case), if not already completed dur-ing the current outage, shall be performed prior to returnto service.

-2500 EXAMINATION REQUIREMENTS

Components shall be examined as specified in Table 1.Volumetric and surface examinations shall be qualifiedin accordance with the low rigor requirements ofArticle 14 of Section V. If obstructions or limitationsprevent examination of the volume or surface requiredby Fig. 2 for one or more nozzles, the analysis procedureof Appendix I shall be used to demonstrate the adequacyof the examination volume or surface for each such noz-zle. If Appendix I is used, the evaluation shall be submit-ted to the regulatory authority having jurisdiction at theplant site.

-3000 ACCEPTANCE STANDARDS

-3100 EVALUATION OF EXAMINATIONRESULTS

-3130 INSERVICE VOLUMETRIC ANDSURFACE EXAMINATIONS

-3131 General(a) The volumetric and surface examinations required

by -2500 and performed in accordance with IWA-2200shall be evaluated by comparing the examination resultswith the acceptance standards in -3132.1, except where-3131(b) is applicable.

(b) When flaws are detected by a required volumetricor surface examination, the component is acceptable forcontinued service provided the requirements ofIWB-3112(b) are met.

(c) Volumetric and surface examination results shallbe compared with recorded results of the preservice exam-ination and prior inservice examinations. Acceptance ofcomponents for continued service shall be in accordancewith -3132.

SUPP 8 - NC 2 (N-729-1)

CASES OF ASME BOILER AND

W -3132 Acceptance-3132.1 Acceptance by Volumetric or Surface

Examination(a) A component whose volumetric or surface exami-

nation confirms the absence of flaws shall be acceptablefor continued service.

(b) A component whose surface examination detectslinear indications of any size, or rounded indications ifother relevant conditions indicate nozzle leakage existson the partial-penetration weld shall be corrected in accor-dance with the provisions of -3132.2.

E (c) A component with planar flaws in the nozzle basemetal shall be corrected in accordance with the provisionsof -3132.2 or -3132.3. Linear indications detected bysurface examination of the nozzle base material shall beconsidered planar. Prior to evaluation, the depth of linearindications shall be further characterized by volumetricexamination. If volumetric examination cannot be per-formed, the linear indication shall be assumed to be planarand through-wall.

-3132.2 Acceptance by Repair/Replacement Acti-vity. A component whose volumetric or surface examina-tion reveals a leak or flaw not acceptable for continuedservice in accordance with the provisions of -3132.3 isunacceptable for continued service until the additionalexams of -2430 are satisfied and the component is cor-rected by a repair/replacement activity to the extent nec-essary to meet the acceptance standards of -3000.

-3132.3 Acceptance by Analytical Evaluation. Acomponent whose volumetric examination detects planarflaws or whose surface examination detects linear indica-tions which are assumed to be planar, is acceptable forcontinued service without repair/replacement activity ifan analytical evaluation meets the requirements of1WB-3660 of the 2004 Edition. The area containing theflaw shall be reexamined in accordance with -2420(a)

O and (b).

-3140 INSERVICE VISUAL EXAMINATIONS(VE)

-3141 General(a) The VE required by -2500 and performed in accor-

dance with IWA-2200 and the additional requirementsof this Case shall be evaluated by comparing the examina-tion results with the acceptance standards specified in-3142.1.

(b) Acceptance of components for continued serviceshall be in accordance with -3142.

(c) Relevant conditions for the purposes of the VEshall include areas of corrosion, boric acid deposits, dis-coloration, and other evidence of nozzle leakage.

CASE (continued)

PRESSURE VESSEL CODE N-729-1-3142 Acceptance

-3142.1 Acceptance by VE(a) A component whose VE confirms the absence of

relevant conditions shall be acceptable for continuedservice.

(b) A component whose VE detects a relevant condi-tion shall be unacceptable for continued service untilthe requirements of -3142.1 (b)(1), (b)(2), and (c) beloware met.

(1) Components with relevant conditions requirefurther evaluation. This evaluation shall include determi-nation of the source of the leakage and correction of thesource of leakage in accordance with -3142.3.

(2) All relevant conditions shall be evaluated todetermine the extent, if any, of degradation. The boricacid crystals and residue shall be removed to the extentnecessary to allow adequate examinations and evaluationof degradation, and a subsequent VE of the previouslyobscured surfaces shall be performed, prior to return toservice, and again in the subsequent refueling outage.Any degradation detected shall be evaluated to determineif any corrosion has impacted the structural integrity ofthe component. Corrosion that has reduced componentwall thickness below design limits shall be resolvedthrough repair/replacement activity in accordance withIWA-4000.

(c) A nozzle whose VE indicates relevant conditionsindicative of possible nozzle leakage shall be unaccept-able for continued service unless it meets the requirementsof -3142.2 or -3142.3.

-3142.2 Acceptance by Supplemental Examination.A nozzle with relevant conditions indicative of possiblenozzle leakage shall be acceptable for continued serviceif the results of supplemental examinations [-3200(b)]meet the requirements of -3130.

-3142.3 Acceptance by Corrective Measures orRepair/Replacement Activity

(a) A component with relevant conditions not indica-tive of possible nozzle leakage is acceptable for continuedservice if the source of the relevant condition is correctedby a repair/replacement activity or by corrective mea-sures necessary to preclude degradation.

(b) A component with relevant conditions indicative ofpossible nozzle leakage shall be acceptable for continuedservice if a repair/replacement activity corrects the defectin accordance with IWA-4000.

-3200 SUPPLEMENTAL EXAMINATIONS

(a) Volumetric or surface examinations that detectflaws which require evaluation in accordance with -3130may be supplemented by other techniques to characterizethe flaw (i.e., size, shape, and orientation).

E

3 (N-729-1) SUPP 8 - NC

CASE (continued)


(b) The supplemental examination performed to sat-isfy -3142.2 shall include volumetric examination of thenozzle tube and surface examination of the partial-pene-tration weld, or surface examination of the nozzle tubeinside surface, the partial penetration weld, and nozzletube outside surface below the weld, in acccordance withFig. 2, or the alternative examination area or volumeshall be analyzed to be acceptable in accordance withAppendix I. The supplemental examinations shall be usedto determine the extent of the unacceptable conditions andthe need for corrective measures, analytical evaluation, orrepair/replacement activity.

-9000 GLOSSARY

bounding loss of coolant accident conditional core dam-age probability (CCDP): the plant-specific conditional

core damage probability for the loss of coolant accident(e.g., medium, small, or small-small break) that boundsthe consequences of the head nozzle-ejection event.

effective degradation years (EDY): the lifetime accumu-lated effective time at temperature, normalized to1059.67R (588.71K), with an activation energy character-istic of initiation of Primary Water Stress CorrosionCracking in UNS N06600, 50 kcal/mol (209 kJ/mol).

reinspection years (RIY): the accumulated effective timeat temperature between examinations normalized to1059.67R (588.7 1K), with an activation energy character-istic of growth of Primary Water Stress Corrosion Crack-ing in UNS N06600, 31 kcal/mol (130 kJ/mol).

SUPR 8 - NC 4 (N-729-1)

0 0 •

TABLE 1 EEXAMINATION CATEGORIES

CLASS 1 PWR REACTOR VESSEL UPPER HEAD

Examination Deferral ofItem Requirements/ Examination Acceptance Examination toNo. Parts Examined Fig. No. Method Standard Extent and Frequency of Examination End of Interval

B4.10 Head with UNS N06600 nozzles and UNS Fig. 1 Visual, VE -3110 Each refueling outage (3), (4) Not permissibleN06082 or UNS W86182 partial penetra- (1), (2)tion welds

B4.20 UNS N06600 nozzles and UNS N06082 or Fig. 2 (5) Volumetric (6) -3130 All nozzles, every 8 calendar years or Not permissibleUNS W86182 partial-penetration welds in Surface (6) -3140 before RIY=2.25, whichever is lesshead - (7), (8), (9), (10)

B4.30 Head with nozzles and partial-penetration Fig. 1 Visual, VE -3110 Every third refueling outage or 5 calendar Not permissiblewelds of PWSCC-resistant materials (1), (2) years, whichever is less (3)

84.40 Nozzles and partial-penetration welds of Fig. 2 (5) Volumetric (6) -3130 All nozzles, not to exceed one inspection Not permissiblePWSCC-resistant materials in head Surface (6) -3140 interval (nominally 10 calendar years)

(8), (10)

NOTES:(1) The VE shall consist of the following:

(a) A direct examination of the bare-metal surface of the entire outer surface of the head, including essentially 100% ofthe intersection of each nozzle with the head. If welded or bolted obstructions are present (i.e., mirror insulation,insulation support feet, shroud support ring/lug), the examination shall include 2>95% of the area in the region of thenozzles as defined in Fig. 1 and the head surface uphill and downhill of any such obstructions. The examination maybe performed with insulation in place using remote equipment that provides resolution of the component metal surfaceequivalent to a bare-metal direct examination.

(b) The examination may be performed with the system depressurized.(c) The examination shall be performed with an illumination level and a sufficient distance to allow resolution of lower case

characters not greater than 0ý105 in. (2.7 mm) in height.(2) Personnel performing the VE shall be qualified as a VT-2 visual examiner and shall have completed at least four (4) hr of

additional training in detection of borated water leakage from UNS N06600, UNS N06082 or UNS W86182 componentsand the resulting boric acid corrosion of adjacent ferritic steel components.

(3) Examination may be performed with the system depressurized.(4) If EDY < 8 and no flaws unacceptable for continued service under -3130 or -3140 have been detected, the reexamination

frequency may be extended to every third refueling outage or 5 calendar years, whichever is less, provided an IWA-2212 VT-2visual examination of the head is performed under the insulation through multiple access points in outages that the VE is notcompleted. This IWA-2212 VT-2 visual examination may be performed with the reactor vessel depressurized.

(5) If the examination area or volume requirements of Fig. 2 cannot be met, the alternative requirements of Appendix I shall be

C used and the evaluation shall be submitted to the regulatory authority having jurisdiction at the plant site.

0

oi

10

'0

YJoIS

C,

.• I (/

I.S

TABLE 1 EXAMINATION CATEGORIES (CONT'D)

NOTES:

(6) Three levels of volumetric and surface examination are allowed (for Item B4.20, see [Note (9)] for effect of each level on

reexamination frequency):(a) Level 1: The volumetric examination requirements of Level 3 examination and surface examination of all J-groove0

nozzle welds. •(b) Level 2: The volumetric examination requirements of Level 3 examination and surface examination of > 50% of the

J-groove nozzle welds.(c) Level 3: Volumetric examination > 95% of the required examination volume of the nozzle tubes in the aggregate, or

surface examination of > 95% of the required examination area of the nozzle tubes and the J-groove nozzle welds, inthe aggregate, or a combination of the two. If a surface examination is being substituted for a volumetric examinationonaportionof a nozzle, that surface examination shall be of the inside surface of the volume not examined volumetrically,

Nin combination with either the outside surface of the unexamined volume if the unexamined volume is below the toe ofthe weld [E on Fig. 2] or the surface of the J-groove nozzle weld if the unexamined volume is above the toe of the weld.

(7) If not previously performed, baseline volumetric and surface examinations shall be performed.(a) for plants with EDY > 12, at the next refueling outage,(b) for plants with EDY Ž 8 and EDY 5 12, no later than the second refueling outage, or,(c) for plants with EDY < 8, no later than February 10, 2008.

(8) If flaws have previously been detected that were unacceptable for continued service in accordance with -3132.3 or that werecorrected by a repair/replacement activity of -3132.2 or -3142.3(b), the reexamination frequency is the more frequent ofthe normal reexamination frequency (before RIY=2.25) or every second refueling outage, and [Note (9)] does not apply.Additionally, repaired areas shall be examined during the next refueling outage following the repair.

(9) Reexamination may be extended to RIY =3, not to exceed nominal 10 calendar years, if either of the following apply:(a) previous examination was Level 1, or(b) previous examination was Level 2 and plant-specific bounding LOCA CCDP < 5 X 10-3

(10) Includes essentially 100% of surface or volume.

0 0 0 0

CASE (continued)


Support lug

Shroud

Flange

Control rod drives

-Service structure

Insulation

Shroud

Aobstruct -area on head outer surface obstructed within D,

A - ,obstruct > 0.95A

FIG. I PWR REACTOR VESSEL UPPER HEAD EXTENT OF VISUAL EXAMINATION E

7 (N-729-1) SUPP 8 - NC

CASE (continued)


Alloy 600/690 nozzle

a = 1.5 in. (38 mm) for Incidence Angle, 0, < 30 deg and for all nozzles > 4.5 in. (115 mm) OD or 1 in. (25 mm) for IncidenceAngle, 0, > 30 deg; or to the end of the tube, whichever is less

A-B-C-D = Extent of volumetric examination for the tube (base metal)A-D = Extent of surface examination for the tube inside surfaceG-F = 1/4 in. (6 mm) from the theoretical point "F" in accordance with the design drawings, including tolerances, unless the point

"F" can be physically determined.G-F-E-C = Extent of surface examination for the J-groove weld (filler metal and buttering) and tube outside surface below the weld

G-F-E = Extent of surface examination zone for the J-groove weld (filler metal and buttering)

FIG. 2 EXAMINATION VOLUME FOR NOZZLE BASE METAL AND EXAMINATION AREAFOR WELD AND NOZZLE BASE METAL

SUPP 8 - NC 8 (N-729-1)

CASE (continued)


MANDATORY APPENDIX IANALYSIS PROCEDURE FOR ALTERNATIVE

EXAMINATION AREA OR VOLUME DEFINITION

1-1000 SCOPE

This Appendix provides an analysis procedure thatshall be used to define an alternative examination areaor volume (zone) to that defined in Fig. 2 if impediments(such as physical obstructions, threads on the nozzle end,or an ultrasonic examination corner shadow zone) preventexamination of the complete zone. In such cases, analysesshall be performed to demonstrate that there is anextremely low probability of PWSCC existing wholly inthe unexamined zones, and that the potential undetectedPWSCC will not lead to a safety concern or an unaccept-able probability of leakage in the time interval until thenext examination.

For alternative examination zones that eliminate por-tions of Fig. 2 examination zone above the J-groove weld(Fig. 1-1), the analyses shall be performed using at leasttwo of the three techniques below to demonstrate thatthe applicable criteria are satisfied. For alternative exami-nation zones that eliminate portions of Fig. 2 examinationzone below the J-groove weld (Fig. 1-2), the analyses shallbe performed using at least the stress analysis method(1-2000) or the deterministic fracture mechanics analysismethod (1-3000) to demonstrate that the applicable crite-ria are satisfied.

All other examination requirements of Table 1 shallbe met.

E 1-2000 STRESS ANALYSIS

This analysis shall be used to determine a reducedexamination zone. Plant-specific analysis shall demon-strate that the hoop and axial stresses on the nozzle insideand outside surfaces remain below 20 ksi (140 MPa)(tensile) over the entire region outside the alternativeexamination zone but within the examination zonedefined in Fig. 2. The analysis shall be performed usingeither design or as-built weld dimensions for the specificnozzles for which a portion of Fig. 2 examination zoneis being eliminated, or for nozzles shown to bound thestresses in those specific nozzles.

1-3000 DETERMINISTIC FRACTUREMECHANICS ANALYSES

The analyses described in 1-3100 or 1-3200 shall beused to determine a reduced examination zone.

1-3100 ZONES ABOVE THE J-GROOVE WELD

For alternative examination zones above the J-grooveweld, the analysis shall demonstrate that a potential cir-cumferential crack in the unexamined zone will not growto a size that exceeds the acceptance criteria for austeniticpiping in IWB-3640 prior to the next scheduled exami-nation.

The crack growth calculation shall be performed basedon the following:

(a) The assumed initial flaw size shall be a through-wall, circumferentially-oriented crack equal to 30 deg ofthe nozzle circumference, at the outermost edge of thealternative examination zone (Fig. 1-1).

(b) Alternatively, the flaw shall be assumed to existin a plane closer to the J-groove weld (i.e., within theinspected region), if such location can be shown to conser-vatively bound flaws at the outermost edge of the alterna-tive examinaton zone.

(c) The flaw shall be assumed to be at either the uphillor the downhill location of the nozzle, whichever resultsin the higher applied stress intensity factor (Fig. 1-1).

(d) The average of inside and outside surface axialstress shall be applied along the entire length of theassumed through-wall crack.

(e) The stress intensity factor for a circumferential,through-wall crack in a cylinder shall be used.

(f) Crack growth rate determination shall be in accor-dance with Appendix 0 of Section XI, in the 2004Edition.

1-3200 ZONES BELOW THE J-GROOVE WELD

For alternative examination zones below the J-grooveweld, the analysis shall demonstrate that a potential axial

9 (N-729-1) SUPP 8 - NC

CASE (continued)


crack in the unexamined zone will not grow to the toeof the J-groove weld prior to the next scheduled exami-nation.

(a) Method 1. Using stress analysis results for the as-designed J-groove weld configuration, demonstrate thatthe upper extremity of an axial through-wall crack wouldnot propagate to the toe of the J-groove weld prior to thenext scheduled examination.

The crack growth calculation shall be performed basedon the following:

(1) The initial axial through-wall crack size shallbe determined by assuming its upper extremity to beinitially located at the bottom edge of the alternativeexamination zone and the lower extremity to be locatedwhere either the inside or the outside surface hoop stressbecomes compressive (Fig. 1-2).

(2) If the hoop stress remains tensile for the entireportion of the nozzle below the weld, an axial through-wall crack shall be postulated from the bottom edge ofthe alternative examination zone to the bottom of thenozzle (Fig. 1-3).

(3) The average of inside and outside surface hoopstresses shall be applied along the entire length of theassumed through-wall crack.

(4) The postulated axial flaw shall be located in theunexamined zone at the azimuthal location that resultsin the shortest time to reexamination.

(5) The stress intensity factor for an axial through-wall crack in a cylinder shall be used.

(6) Crack growth rate determination shall be inaccordance with Appendix 0 of Section XI, in the 2004Edition.

(b) Method 2. If acceptability cannot be demonstratedusing Method 1, the following shall be performed.

(1) Review the available UT examination data anddemonstrate that the as-built J-groove weld depth is largerthan the as-designed weld depth.

(2) Determine the hoop stress distribution in theportion of the nozzle below the weld by performing astress analysis based on the as-built J-groove weld con-figuration.

(3) Perform the crack growth calculation of Method1, using the hoop stress distribution for the as-built con-figuration.

1-4000 PROBABILISTIC FRACTUREMECHANICS ANALYSIS

These provisions shall not be applied to heads havingprior PWSCC in nozzles or J-groove welds that requiredrepair/replacement activity. Calculate the percentage ofthe total required examination zone defined in Fig. 2, forall nozzles in the head, that will be eliminated. Demon-strate, using a probabilistic fracture mechanics method,that the total eliminated examination zone in all nozzlesdoes not lead to unacceptable probabilities of leakageand nozzle ejection prior to the next required examination.A probability of leakage no greater than 5% per vesselper year and a probability of core damage associated withthe potential for nozzle ejection no greater than 1 X 10-6

per vessel per year are acceptable.

SUPP 8 - NC 10 (N-729-1)

CASE (continued)


. Nozzle

Postulatedcircumferentialcrack assumptions(30 deg uphill or downhillthrough-wall cracks) -

RPV head

zone aboveweld

Examination

FIG. I-1 CIRCUMFERENTIAL FLAW ASSUMPTION FOR ELIMINATION OF PORTIONS OF THE REQUIREDEXAMINATION ZONE ABOVE J-GROOVE WELD

11 (N-729-1) SUPP 8 - NC

CASE (continued)


0Nozzle

RPV head

Examinationzone

Unexamined zonebelow weld

Permissiblecrack growth -

to edge of weld

Postulated regionthrough-wallcrack below weld

FIG. 1-2 AXIAL FLAW ASSUMPTION FOR ELIMINATION OF PORTIONS OF THE REQUIRED EXAMINATION ZONEBELOW J-GROOVE WELD

0

0

SUPP 8 - NC 12 (N-729-1)

CASE (continued)


Nozzle

RPV head

Examinationzone

Unexamined zonebelow weld

Permissiblecrack growth -to edge of weld

Postulated through-wallcrack below weld

FIG. 1-3 AXIAL FLAW ASSUMPTION FOR ELIMINATION OF PORTIONS OF THE REQUIRED EXAMINATION ZONEBELOW J-GROOVE WELD (TENSILE STRESS TO BOTTOM OF NOZZLE)

13 (N-729-1) SUPP 8 - NC

case vessel code n-729-1 2005. this means that · case cases of asme boiler and pressure vessel...

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